1. Field of the Invention
The present invention generally relates to data storage and, more specifically, to systems and methods for controlling the voltage on the lens of electron emitters in atomic resolution storage (ARS) devices.
2. Description of the Related Art
The apparent insatiability of consumers for higher capacity, higher speed memory storage devices has led to the development of memory storage techniques such as atomic resolution storage (ARS). As is Known, a storage device employing ARS technology includes a number of electron emitters, such as field emitters, for example, that are adapted to write data to and read data from various storage areas of a storage medium.
During operation, an electron beam current is extracted from an emitter towards a corresponding storage area. Writing of data from an emitter to a storage area is accomplished by temporarily increasing the power density of the electron beam current to modify the structural state of the surface of the storage area. In contrast, reading data from the storage area is accomplished by observing the effect of the storage area on the electron beam of the emitter, or the effect of the electron beam on the storage area. More specifically, reading typically is accomplished by collecting secondary and/or backscattered electrons when an electron beam, i.e., an electron beam with a lower power density than that of the electron beam utilized for writing data to the storage area, is applied to the storage medium.
An ARS storage medium is formed of material characterized by a structural state that can be changed from crystalline to amorphous by a beam of electrons. Since the amorphous state has a different secondary electron emission coefficient (SEEC) and backscattered electron coefficient (BEC) than the crystalline state, a different number of secondary and backscattered electrons are emitted from each storage area in response to an electron beam, depending upon the current structural state of that storage area. Thus, by measuring the number of secondary and backscattered electrons, the structural state of the storage area and, therefore, the data stored by the storage area, may be determined.
A problem with emitters is in controlling the focal point of the emitted beam. If the beam is not properly focused, writing operations may fail, which may result in data being lost. Similarly, an improperly focused beam may hamper or even prohibit reading operations as well. Thus, there is a need for a system and method to control the focal point of the emitted beam for a plurality of electron emitters in an ARS.
Another problem is that it is difficult to physically locate emitter circuitry proximate to the emitters that are being controlled due to space limitations of the individual electrical components. Typically, the silicon area under the emitter is limited and usually reserved for emitter control circuitry, which has the highest priority for this area. Thus, there is a need for a system and method to remove certain electrical components and related circuitry from underneath the emitters while still controlling the focal point of the emitted beam of all electron emitters in an ARS.